MOSCOW -- It was a historic summit, but neither Mikhail S. Gorbachev nor George Bush was invited.

Russian President Boris N. Yeltsin signed a treaty with Lithuania yesterday effectively recognizing its declared independence and agreeing to broad areas of economic cooperation. It was an important boost for beleaguered Lithuania, a further assertion of power for Mr. Yeltsin, and a most unwelcome complication for President Bush's host.

Mr. Gorbachev has been negotiating a new Union Treaty with nine of the 15 republics, leaving unclear the fate of the six secessionist states, including Lithuania, which declared independence in March 1990.

Now, with recognition by Russia, the Soviet government may "move out of its stall and start real negotiations with Lithuania" on separation, Lithuanian President Vytautas Landsbergis said.

The signing occurred just a few hundred yards from the flashy Mezhdunarodnaya Hotel, where part of the Bush entourage is staying. It demonstrated just how complicated political authority has become in the Soviet Union, where power once flowed neatly down from the top.

Mr. Yeltsin, who won a resounding victory at the polls this spring when he was elected Russia's president, is more and more asserting his clout.

Last week he banned Communist Party cells from Russia's workplaces, and yesterday he dared Mr. Gorbachev to do something about it.

Before the signing ceremony yesterday, Mr. Yeltsin also received an unprecedented invitation from Mr. Gorbachev to participate in the summit with President Bush. Mr. Yeltsin later said that he would be happy to meet Mr. Bush and that he would consider it a meeting of equals -- one national president talking to another.

A similar invitation went to President Nursultan Nazabayev of Kazakhstan.

A second assertion of the republics' power also surfaced yesterday. The newspaper Kommersant reported that all 15 of the Soviet republics have worked out a deal to share Soviet diamond, gold and hard currency reserves, and also take on the nation's foreign debt of $65 billion, effectively bypassing the central government.

There was no word on how the republics actually intended to take possession of all the assets they are agreeing to divide up.

But in any case the Kommersant report only served to highlight the complications Mr. Bush faces in trying to do business with the Soviet Union. For years it was American presidents who explained that they were powerless to force Congress' hand. Now it is Mr. Gorbachev who is president of a nation that also includes 15 increasingly assertive republican presidents, of varying temperaments and levels of hostility toward Moscow.

Mr. Bush, for his part, has endorsed the claims of Lithuania and the other Baltic republics, but he has carefully tried to act as though Mr. Gorbachev were in charge. He told Soviet journalists that there was no "triangle" connecting the White House, the Soviet central government and the various republics.

But in addition to his meetings with Mr. Yeltsin and Mr. Nazabayev, Mr. Bush is also flying to Kiev Thursday, where he will talk with the Ukrainian president, Leonid Kravchuk. Mr. Gorbachev will not go along.

Yesterday's treaty signing, in the glare of international attention heightened by the interest in that other summit -- Mr. Bush's and Mr. Gorbachev's -- was not the first among Soviet republics. Russia, for instance, has signed pacts with Estonia and Latvia. But negotiations had dragged on between Mr. Yeltsin's government and Lithuania, the least compromising of the Baltic republics, until suddenly this week the obstacles were swept away.

In the treaty that was finally reached, Russia also pledged not to allow its armed forces to be used against Lithuania. In return Lithuania relented on its earlier insistence on ethnic purity and granted rights of citizenship to Russians and others who were living in the republic before 1989.

Mr. Landsbergis -- who arrived at the Russian government building in a big black Cadillac -- said he hoped Russia would help remove the KGB from Lithuanian soil. Aleksandr Rutskoi, the Communist vice president of Russia, later said the republic was intent on at least removing Russian soldiers now serving in Lithuania.

He described the Soviet attack on the Vilnius television center this winter, which left 15 people dead, as a "gangster action," the Baltfax news agency reported.